Ajahn (Thai: อาจารย์, RTGS: 'achan', IPA: [ʔāː.tɕāːn], also romanized ajaan, ajarn, acharn and achaan) is a Thai language term which translates as "teacher". It is derived from the Pali word ācariya, and is a term of respect, similar in meaning to the Japanese sensei, and is used as a title of address for high-school and university teachers, and for Buddhist monks who have passed ten vassa.This lattermost case is usually romanized ajahn. According to the Vinaya, any properly ordained monk can become an ācariya after ten vassa in the robes, thus a Thai monk becomes ajahn.A senior monk may bear the honorific title phra ajahn (Thai: พระอาจารย์,"venerable monk"), or in more informal situations, than ajahn (Thai: ท่านอาจารย์,"venerable monk").[1]-- http://en.wikipedia.org/wiki/Ajahn

Bhante (Pali; Nepali; Burmese: ဘန္တေ, pronounced: [bàɴtè], Sanskrit: vande and vandanā[1]) is the polite particle used to refer to Buddhist monks in the Theravada tradition. Bhante literally means "Venerable Sir."[2] The Nepali terms for the Buddhist priestly caste, bare and bande, have the same derivation.[3]-- http://en.wikipedia.org/wiki/Bhante

kind regards,

Ben

“No lists of things to be done. The day providential to itself. The hour. There is no later. This is later. All things of grace and beauty such that one holds them to one's heart have a common provenance in pain. Their birth in grief and ashes.” - Cormac McCarthy, The Road

Learn this from the waters:in mountain clefts and chasms,loud gush the streamlets,but great rivers flow silently.- Sutta Nipata 3.725

If you have asked me of the origination of unease, then I shall explain it to you in accordance with my understanding: Whatever various forms of unease there are in the world, They originate founded in encumbering accumulation. (Pārāyanavagga)

Exalted in mind, just open and clearly aware, the recluse trained in the ways of the sages:One who is such, calmed and ever mindful, He has no sorrows! -- Udana IV, 7

Actually it is derived from the Sanskrit word ācārya which is obvious from the Thai spelling. Sanskrit was used perhaps more extensively in SE Asia and many words in native languages are adopted from from Sanskrit terms. Pali was reserved for monastic use mainly. So an "ajahn" or "ajaan" or "acharn" would not necessarily mean a monk with a minimum of 10 Vassas who can give dependence to a junior monk and be his mentor. The term is used rather more loosely now.

(Sri Lankan monks who have spent time in Thailand are starting to called themselves "Ajahn So-and-so" which sounds rather funny.)

in my local temples, I seem to remember Ajahn refering to just the head monk of a temple, not just any senior monk, at the one temple with vietnamese/lao roots the head monk was lunpo, I think.

18 years ago I made one of the most important decisions of my life and entered a local Cambodian Buddhist Temple as a temple boy and, for only 3 weeks, an actual Therevada Buddhist monk. I am not a scholar, great meditator, or authority on Buddhism, but Buddhism is something I love from the Bottom of my heart. It has taught me sobriety, morality, peace, and very importantly that my suffering is optional, and doesn't have to run my life. I hope to give back what little I can to the Buddhist community that has so generously given me so much, sincerely former monk John

Just regional conventions. 'Bhikkhu' before the name is the norm in Sri Lanka and Burma; 'bhikkhu' after the name is the norm in Thailand, Laos and Cambodia. That's assuming the word bhikkhu is used at all, which isn't always the case; in Asia one more often finds 'thera' or some regional title such as 'chao khun' or 'sayadaw' used instead.